1. Field of the Invention
The present invention relates generally to thin-film magnetic write heads for use in, for example, floating thin-film magnetic heads. Particularly, the present invention relates to a thin-film magnetic head having a small gap depth (Gd), which is free from side writing.
2. Description of the Related Art
FIG. 28 is a longitudinal sectional view of a conventional thin-film magnetic write head. As shown in FIG. 28, the conventional thin-film magnetic write head comprises a lower core layer 10 made of a magnetic material such as a NiFe alloy and a gap layer 11 made of Al2O3 or SiO2 formed on the lower core layer 10.
Referring to FIG. 28, a gap depth (Gd) defining layer 12 is formed at a position on the gap layer 11 a predetermined distance L1 behind in the height direction, i.e., the Y direction in the drawing, relative to the face opposing a recording medium. The Gd defining layer 12 is composed of an organic insulative material such as resist, for example. The predetermined distance L1 is the gap depth (Gd).
Referring to FIG. 28, an upper magnetic pole layer 13 made by plating using a magnetic material such as a NiFe alloy extends from the face opposing the recording medium to the top of the Gd defining layer 12 while overlaying the gap layer 11 and the Gd defining layer 12 with a plating base layer 13a therebetween. An insulating layer 14 composed of Al2O3 or the like is formed behind the upper magnetic pole layer 13 in the height direction.
A coil layer (not shown) is formed on the insulating layer 14, and an insulating layer 18 composed of an organic insulative material or the like is formed on the insulating layer 14 so as to cover the coil layer.
Referring to FIG. 28, an upper core 15 is plated over the upper magnetic pole layer 13, the insulating layer 14, and the insulating layer 18 using a magnetic material such as a NiFe alloy.
FIG. 29 is a perspective view showing the structure of the vicinity of the face of the thin-film magnetic head opposing the recording medium shown in FIG. 28. The drawing of FIG. 29 is a schematic illustration and the upper core 15, for example, is omitted from the drawing.
As shown in FIG. 29, the lower core layer 10 at the two sides of the upper magnetic pole layer 13 in the track width direction, i.e., the X direction in the drawing, is milled to form recesses 16.
Referring to FIG. 29, a lower magnetic pole section 10a protruding from the upper surface of the lower core layer 10 is formed under the Gd defining layer 12. The lower magnetic pole section 10a is also under the upper magnetic pole layer 13. The width of the lower magnetic pole section 10a in the track width direction at a position below the upper magnetic pole layer 13 is the same as the track width Tw and is substantially the same as the width of the upper magnetic pole layer 13.
In this conventional head, a recording magnetic field is mainly generated between the upper magnetic pole layer 13 and the lower magnetic pole section 10a and leaks from the face of the head opposing the recording medium. Since the lower magnetic pole section 10a protrudes from the surface of the lower core layer 10 toward the upper magnetic pole layer 13, top faces 10b of the lower core layer 10 are distant from the upper magnetic pole layer 13. This distance promotes generation of a recording magnetic field between the upper magnetic pole layer 13 and the lower magnetic pole section 10a, both having the track width Tw, thereby suitably inhibiting the occurrence of side fringing.
Trends toward higher recording densities demand narrower tracks and smaller gap depths. In order to prevent magnetic saturation, decrease in recording current is also necessary. Since a combination of a large gap depth (Gd) and decreased recording current causes drastic reduction in magnetic flux generated between the upper magnetic pole layer 13 and the lower magnetic pole section 10a, the gap depth (Gd) is preferably small.
In view of the above, conventionally, the Gd defining layer 12 is arranged near the face opposing the recording medium so as to shorten the gap depth L1, as shown in FIG. 29. The gap depth L1 is, for example, 0.6 xcexcm or less.
However, the thin-film magnetic head shown in FIG. 29, which has a decreased gap depth L1, suffers from the following problems.
Referring to FIG. 29, the Gd defining layer 12 protrudes from the two sides of the upper magnetic pole layer 13 in the track width direction, i.e., the X direction in the drawing. The protruding Gd defining layer 12 functions as a mask for forming the recesses 16 by milling the lower core layer 10 with ions and allows the portion of the lower core layer 10 under the Gd defining layer 12 to remain intact during milling with ions. Thus, similarly to the Gd defining layer 12, the resulting lower magnetic pole section 10a protrudes from the two sides of the upper magnetic pole layer 13 in the track width direction. The portion of the lower core layer 10 protruding from a side of the upper magnetic pole layer 13 is referred to as a protuberance 10a1. The distance between the face opposing the recording medium and the protuberance 10a1 is substantially the same as the gap depth, which is represented by L1.
Since the protuberance 10a1 under the Gd defining layer 12 protrudes from the upper magnetic pole layer 13 in the track width direction, the protuberance 10a1 has a large cross-section taken in the direction parallel to the face opposing the recording medium. As a result, the demagnetizing field is strong at the protuberance 10a1.
At a large gap depth L1, the demagnetizing field of the protuberance 10a1 hardly causes any problem because the protuberance 10a1 is distant from the face opposing the recording medium in the height direction, i.e., the Y direction in the drawing. However, at a small gap depth L1, the distance between the protuberance 10a1 and the face opposing the recording medium is decreased, resulting in generation of a leakage magnetic field between the upper magnetic pole layer 13 and the protuberance 10a1.
Since the width of the protuberance 10a1 in the track width direction is larger than the track width Tw, the protuberance 10a1 also writes data and thus cause side writing.
FIG. 30 is a graph showing a track profile, i.e., an output profile in the cross-track direction, taken by actually reading data written on a recording medium using a magnetoresistive (MR) head comprising the thin-film magnetic head shown in FIG. 29. In this experiment, data was recorded using the thin-film magnetic head having a skew angle, i.e., an inclination with respect to the tangential direction of the motion of the recording medium, and was read using the MR head.
As shown in FIG. 30, the read waveform has a peak A and a noise waveform B at a side of the peak A. The noise waveform B demonstrates that the upper magnetic pole layer 13 and the protuberance 10a1 caused side writing.
Side writing causes degradation, such as the generation of noise, in recording characteristics. In other words, as shown in FIG. 29, the conventional thin-film magnetic head comprising the Gd defining layer 12 and the lower magnetic pole section 10a formed by milling the surface of the lower core layer 10 cannot achieve both small gap depth and inhibition of side writing.
The present invention aims to solve the above-described problems of the conventional art. An object of the present invention is to provide a thin-film magnetic head having a narrower track width required for higher recording densities while suitably preventing side writing. Another object of the present invention is to provide a manufacturing method for such a thin-film magnetic head.
The present invention provides a thin-film magnetic head comprising: a lower core layer comprising a lower magnetic pole section which extends in a height direction from an opposing face of the thin-film magnetic head opposing a recording medium and protrudes from an upper surface of the lower core layer; a gap layer formed on the lower core layer; an upper magnetic pole layer formed on the gap layer, the upper magnetic pole layer having a width smaller than that of the lower core layer; an upper core layer formed on the upper magnetic pole layer and above the gap layer; and a gap depth defining layer formed above the lower magnetic core layer and under the upper magnetic pole layer below the upper core layer, the gap depth defining layer being disposed a predetermined distance behind the opposing face. Two side faces of the gap depth defining layer and two side faces of the lower magnetic pole section in a track width direction are flush with two side faces of the upper magnetic pole layer and the two side faces of the upper core layer in the track width direction at at least a front portion of the layers that is close to the opposing face.
In a conventional magnetic head, the lower magnetic pole section protrudes in the track width direction from the two sides of the upper magnetic pole layer. In the present invention, at at least the front portion close to the opposing face, the lower magnetic pole section does not protrude from the sides of the gap depth defining layer, and the two side faces of the lower magnetic pole section and the two side faces of the gap depth defining layer are flush with the two side faces of the upper core layer.
As a result, in the present invention, side writing can be suitably prevented even at a small gap depth defined by the distance from the front end of the gap depth defining layer to the opposing face because of the above structure. Thus, a thin-film magnetic head free of side writing and having superior recording characteristics can be provided.
In the present invention, the length of the lower magnetic pole section at the front portion is preferably at least 0.6 xcexcm in order to suitably prevent side writing.
In the present invention, the gap layer may be formed on the lower magnetic pole section, and the gap depth defining layer preferably comprises an insulative material comprising at least one selected from the group consisting of AlO, Al2O3, SiO2, Ta2O5, TiO, AlN, AlSiN, TiN, SiN, Si3N4, NiO, WO, WO3, BN, CrN, and SiON.
In the present invention, the gap depth defining layer may be formed on the lower magnetic pole section, and the gap layer may extend over the lower magnetic pole section and the gap depth defining layer. In such a case, the gap layer preferably comprises a nonmagnetic metal material comprising at least one selected from the group consisting of NiP, NiPd, NiW, NiMo, NiCu, Au, Pt, Rh, Pd, Ru, and Cr.
Preferably, the gap depth defining layer has a substantially semi-elliptic vertical cross-section taken in the height direction and in a direction perpendicular to a bottom face of the lower core layer.
The gap depth defining layer may protrude in the height direction from a back end face of the upper magnetic pole layer, and the protruding portion of the gap depth defining layer may have a flat or curved face tilting in the height direction as the face extends from the upper magnetic pole layer to the lower magnetic pole section.
The thin-film magnetic head of the present invention may further comprise a coil layer formed on the lower core layer with an insulating layer therebetween, the coil layer being formed behind the lower magnetic core layer in the height direction. The coil layer may be covered with the gap depth defining layer, and a front portion of the gap depth defining layer lying in front of the coil layer may have two side faces that are flush with the two side faces of the upper magnetic core layer.
A method for manufacturing the thin-film magnetic head of the present invention comprises the steps of:
(a) forming the gap layer on the lower core layer and forming the gap depth defining layer on the gap layer at a position distant from the opposing face in the height direction;
(b) forming a resist layer on the lower core layer and the gap depth defining layer, and exposing and developing the resist layer to form an opening, the opening having a width smaller than that of the gap depth defining layer in the track width direction and extending from the opposing face to the top of the gap depth defining layer;
(c) forming the upper magnetic pole layer in the opening by plating and removing the resist layer;
(d) removing at least a front portion close to the opposing face of the gap depth defining layer protruding from the two sides of the upper magnetic pole layer in the track width direction and making the two side faces of the resulting gap depth defining layer flush with the two side faces of the upper magnetic pole layer;
(e) removing the gap layer extending at the two sides of the upper magnetic pole layer in the track width direction and milling the surface of the lower core layer exposed by removing the gap layer so as to form the lower magnetic pole section protruding from the upper surface of the lower core layer so as to make the two side faces of a portion of the lower magnetic pole section flush with the two side faces of the upper magnetic pole section and the two side faces of the gap depth defining layer, the portion of the lower magnetic pole section being under the gap depth defining layer having the two side faces flush with the two side faces of the upper magnetic pole layer as a result of step (d); and
(f) forming the upper core layer on the upper magnetic pole layer.
According to this method, the side faces of the gap depth defining layer and the lower magnetic pole section formed under the upper magnetic pole layer can be made flush with the side faces of the upper magnetic pole layer at least at a front portion close to the opposing face.
As a result, a thin-film magnetic head having a small gap depth for higher recording densities and suitably preventing side writing can be manufactured by the above method.
Preferably, the method further comprises step (g) of forming a plating base layer on the lower core layer and gap depth defining layer between step (a) and step (b), and before step (d), the plating base layer formed around the upper magnetic pole layer is removed so as to expose the gap depth defining layer and the gap layer. With such steps, the upper magnetic pole layer can be easily and properly formed by plating.
In the present invention, the gap layer preferably comprises an insulative material comprising at least one selected from the group consisting of AlO, Al2O3, SiO2, Ta2O5, TiO, AlN, AlSiN, TiN, SiN, Si3N4, NiO, WO, WO3, BN, CrN, and SiON.
Another method for manufacturing the thin-film magnetic head of the present invention comprises the steps of:
(h) forming the gap depth defining layer on the lower core layer and behind the opposing face in the height direction;
(i) forming a resist layer on the lower magnetic core layer and the gap depth defining layer and exposing and developing the resist layer so as to form an opening, the opening having a width smaller than the width of the gap depth defining layer in the track width direction and extending from the opposing face up to the top of the gap depth defining layer;
(j) forming the gap layer and the upper magnetic pole layer in the opening by plating and removing the resist layer;
(k) removing at least a front portion of the gap depth defining layer protruding form the two sides of the upper magnetic pole layer in the track width direction and being close to the opposing face so as to make the two side faces of the gap depth defining layer flush with the two side faces of the upper magnetic pole layer;
(l) milling the surface of the lower core layer extending at two sides of the upper magnetic pole layer in the track width direction so as to form the lower magnetic pole section protruding from the top face of the lower core layer, thereby making the two side faces of a portion of the lower magnetic pole section flush with the side faces of the upper magnetic pole layer and the gap depth defining layer, the portion of the lower magnetic pole section being under the gap depth defining layer flush with the side faces of the upper magnetic pole layer through step (k); and
(m) forming the upper core layer on the upper magnetic pole layer.
According to this method also, the side faces of the gap depth defining layer and the lower magnetic pole section formed under the upper magnetic pole layer can be made flush with the side faces of the upper magnetic pole layer at least at a front portion close to the opposing face. As a result, a thin-film magnetic head having a small gap depth for higher recording densities and suitably preventing side writing can be manufactured by the above method.
The gap layer is preferably formed by plating with a nonmagnetic metal material selected from the group consisting of NiP, NiPd, NiW, NiMo, NiCu, Au, Pt, Rh, Pd, Ru, and Cr. With this material, the gap layer and the upper magnetic pole layer can be sequentially plated.
Preferably, in steps (d) and (k), the portions of the gap depth defining layer protruding from the upper magnetic pole layer are removed by RIE or ashing. During these steps, the upper magnetic pole layer may function as a mask so as to selectively remove the protruding portions of the gap depth defining layer by RIE or ashing.
Preferably, in steps (e) and (l), the surface of the lower core layer is milled with ions to form the lower magnetic pole section.